In certain types of apparatus having means for adjustably setting a major number of data, it is sometimes required to reproduce a once-established combination of set valves or adjustment positions. Such apparatus may include a large number of juxtaposed or adjacent slide buttons adapted to move along parallel paths.
For example, in the programmer for timing the control of a mandrel of an extruder in blow-molding apparatus, program data is established by adjusting the positions of a number of juxtaposed slide potentiometers. The settings established by these potentiometers establishes the wall thickness of the extruded parison at various points along its extruded extent. This wall thickness program has to be accurately reproduced by exactly resetting the slide potentiometers, if a given blow-molded body is to be produced again after an interruption by a different program.
In order to duplicate a once-established program, it is of course possible to read and record the positions of the various slide buttons on the potentiometers, in order to reset them to these same positions at a later time. However, such reading, recording and resetting is both troublesome and inaccurate.
To facilitate this resetting step, it is already known to employ a jig made from a sheet of aluminum. Such a jig has been formed to have a plurality of slots, each of which accommodates motion of one potentiometer slide button. The depth of each slot determined the extent of travel of the associated button. Usually, the designed depth of the slot was determined by measurement. This lead to errors and inaccuracies, particularly if the slot was formed to have a depth greater than desired. Another disadvantage was that a separate jig was needed for each different program. It was only practical to modify an existing program by lengthening the extent of the slots.